There is a need to measure non-invasively and accurately a diameter or a sectional area of a blood vessel of a living being, a velocity of a blood flow in a blood vessel, or an amount of a blood flow in a blood vessel, for the purpose of examining the condition of the living being. For example, when the condition of endothelium of an artery having an inner diameter of 4 mm is examined, it is needed to measure, with allowable errors of 1%, a diameter or a sectional area of the artery, a velocity of a blood flow in the artery, or an amount of a blood flow in the artery.
Patent Document 1 proposes non-invasively placing a first array including a plurality of first supersonic-wave elements arranged in one direction, and a second array including a plurality of second supersonic-wave elements arranged in a direction parallel to said one direction, such that the first and second arrays are respectively located at two positions distant from each other in a lengthwise direction of a blood vessel located under a skin of a living being, and detecting respective shapes of respective sections of the blood vessel that correspond to the two positions, respectively. According to this technique, a supersonic wave is utilized and accordingly a sectional shape of a blood vessel can be detected non-invasively.
Patent Document 1: Japanese Patent Application Publication No. 11-76233